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build a cb antenna Matcher?

Discussion in 'Home Brew' started by sanjosebay21, May 26, 2013.

  1. sanjosebay21

    sanjosebay21 Member

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    Does any body know how to build an antenna Matcher for CB radio that can explain or have picture I want to build a small simple one using trimmer pots / air caps?


     

  2. Captain Kilowatt

    Captain Kilowatt Professional Amateur
    Staff Member

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    Google pi network antenna tuner.

    The Pi network is most versatile allowing matching over a wide range. Use something like a pair of 100 or 200 pF caps to ground and a tapped coil in the series leg. Make the coil about 10 turns and about two inches in diameter from 14 gauge wire or larger. Tap the coil at one, two, three, five, eight and ten turns. Should tune more than you would ever encounter on CB.

    [​IMG]

    There are other types of tuners such as the SPC Match (series parallel capacitor) the L network or the T network but the Pi is likely the most useful for what you want.
     
    #2 Captain Kilowatt, May 26, 2013
    Last edited: May 27, 2013
  3. dejaskysdad

    dejaskysdad Member

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    .
     
    #3 dejaskysdad, May 26, 2013
    Last edited: May 27, 2013
  4. Robb

    Robb Yup

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    There is an easier way than building one for yourself; but perhaps not as satisfying as building your own.

    MFJ makes the MFJ-949 tuner that can be had for as cheap as $50/used and will work right now. It also has a built-in cross-needle SWR meter - which is the best way to have an SWR meter - IMO. Not to mention other cool features, such as a built-in antenna switch and other goodies too. Will handle up to 300 watts . . .

    http://www.mfjenterprises.com/Product.php?productid=MFJ-949E

    [​IMG]

    [​IMG]
     
    Tallman likes this.
  5. dc2rf

    dc2rf Active Member

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    This simple tapped L match works well for me. The input from the radio is at the coil end, the output to the antenna is alongside the capacitor.

    I made a coaxial vertical dipole, cut for 11 meters, fed with 50 ohm RG-213. The antenna doesn't present a 1.1 swr match, so I built the tuner to match the antenna to the radio.
     

    Attached Files:

    #5 dc2rf, Jan 17, 2014
    Last edited: Jan 17, 2014
  6. Jimbobre

    Jimbobre New Member

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  7. Jimbobre

    Jimbobre New Member

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    Hi dc2rf i have a half wave dipole that has a swr 1.5. whilw it is not bad, iwould like to bring it down to a 1:1 match. i found your matcher and would like to try it. unfortunatly you do not show much detail. Re the coil size, wire size, length, dia etc. i would like to see a close up of the matcher so as to enable me to build it. I can not remove the antenna as it is up 9 meters. So the easist way is the matcher. Hoping to hear from you soon. Jimbobre
     
  8. The DB

    The DB Sr. Member

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    A half wave dipole has a natural match around 1.5. That is normal for that antenna design, and if it were any lower you would need to look into it and see why.

    Once you get to a certain SWR, getting it lower doesn't actually help you any, and depending on how you get it lower, might actually hurt your signal. You are beyond that point of a safe SWR. If you really want to tune your antenna further you need an antenna analyzer... Or at the least a field strength meter.

    To many people get over obsessed with SWR. Do yourself a favor and don't follow that path.


    The DB
     
    midnight special and Jimbobre like this.
  9. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    I have one of these and it is a great and quick way to reduce your swr readings. This meter is the easiest to use and it is quick.
    A field strength meter and take readings with is the best way to tell you if your antenna is really putting out. I use my spectrum analyzer to monitor signal strength when I tuneup.
    I also have it's BIG Brother MFJ-989 that is rated for 3 KW pep. You can find these cheap if you hunt for a little while.
     
  10. lgwsaw

    lgwsaw Member

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    I know this post is a bit old but I couldn't resist-----I through this together on about 5 minutes and will match anything--even a old rusty steel fence post.
    Link coupled tuner is the way too go.
    Cheers
    N7ZDR Link Coupled Tuner #2.jpg Link Coupled Tuner #2.jpg
     
  11. TheSpaceMann

    TheSpaceMann Active Member

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    Have a parts list and schematic?
     

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